Objective: This case series explored the integration of smartwatches in a community mental health service to support severe mental illness (SMI) management and intervention. We examined whether biometric data provided by smartwatches could help to predict relapse and inform treatment decisions. Method: Four SMI patients were selected from a prior study. Clinicians accessed patients’ biometric data (activity, sleep, heart rate, and electrodermal activity) through smartwatches. Results: Changes in circadian rhythm and electrodermal activity preceded hospitalization in two cases. Additionally, smartwatch data was effectively used to guide targeted interventions, improving patient treatment outcomes. Conclusion: Integrating smartwatches in community mental health services offers promise as adjunct tools for severe mental illness management. However, ethical considerations on data privacy and technology reliance require further evaluation.